Ignition device for monorotor rotary piston internal combustion engines

ABSTRACT

The ignition device includes a rotary switch for preventing the voltage peak which is produced on the closing or opening of the breaker from appearing at the electrodes of the spark plug when the latter is in a combustion chamber of the engine at the beginning of compression. The device may include a cam driven by the engine and having an outline of sudden slope. The device has a disrupting effect sensitive to the direction of flow of the current in the secondary of the ignition coil.

D United States Patent 1 1 1 397359739 Panhard [4 May 29, 1973 154]IGNITION DEVICE FOR MONOROTOR 3,196,846 7/1965 Ohlendorf ..123/8.09ROTARY PISTON INTERNAL 3,576,183 4/1971 Miyamoto ..123/148 E COMBUSTIONENGINES 3,534,717 10/1970 Froede ..123/148 DS 1,928,221 9/1933Fitzsimmons ..123/148 DC [75] Inventor: Jean Panhard, Paris, France1,997,515 4/1935 Finch ..123/148 DC [73] Assignec: Societe deConstructions Mecaniq ,801,608 4/1931 Lee ..123/148 DC Panhard &Lavasson, Paris, France FOREIGN PATENTS OR APPLICATIONS 12 1 Filedl 1970930,623 7/1963 Great Britain ..123/8.09 [21] Appl. No.: 20,661

Primary Examiner-Laurence M. Goodridge Assistant Examiher-Cort R. FlintForelgn Appllcatlon Pnorlty Data Attorney-Waters, Roditi, Schwartz andNissen Mar. 18, 1969 France ..6907680 [57] ABSTRACT [52] 123/148 123/148The ignition device includes a rotary switch for 123/148 E preventingthe voltage peak which is produced on the [51] Int. Cl ..F02p 3/02closing or opening of the breaker f appearing at [58] Fleld of Search..123/l48 E, 148 DC, the electrodes of the Spark plug h the latter i i a123/8091 148 combustion chamber of the engine at the beginning ofcompression. The device may include a cam driven by [56] ReferencesC'ted the engine and having an outline of sudden slope. The UNITEDSTATES PATENTS device has a disruptingeffect sensitive to the directionof flow of the current in the secondary of the ignition 3,584,608 6/1971Shibagaki ..123/8.09 coil, 2,612,879 10/1952 Hibbard ..l23/8.O92,621,312 12/1952 Mascuch ..123/148 A 10 Claims, 5 Drawing Figures SHEET3 OF 3 IGNITION DEVICE FOR MONOROTOR ROTARY PISTON INTERNAL COMBUSTIONENGINES The present invention relates to an ignition device for amonorotor rotary piston internal combustion engine. More particularly itrelates to a device of this type which includes a breaker, a cam drivenby the engine and co-operating with the breaker, an induction coil and aspark plug, said breaker causing, especially on opening, but also onclosing of the primary circuit of the coil, a voltage peak of openingand of closing at the terminals of the secondary circuit of the saidcoil, which is connected to the spark plug.

The invention relates more particularly, because it is in this case thatits application seems to offer the most advantage, but not exclusively,to those of the abovesaid ignition devices which include two spark plugsdisplaced in the peripheral direction and, in general, one inductioncoil and one breaker per spark plug.

As will become apparent from the following description of a conventionalmonorotor rotary piston engine, there can occur through the closingvoltage peak, premature ignition by one of the spark plugs whichdisturbs the smooth operation of the engine.

It is an object of the invention, particularly, to render these devicessuch that their combustion cycles are practically free of suchdisturbance.

The ignition device for the rotary piston internal combustion enginedefined above is characterized, according to the invention, by the factthat it comprises means adapted to prevent voltage peaks of closing fromappearing between the electrodes of the spark plug when this latter isin a combustion chamber of the engine at the beginning of compression.

In a first embodiment, these means are arranged to, on one hand,establish an electrical connection between the spark plug and thesecondary of the coil on opening or immediately before opening of thebreaker, and on the other hand, to interrupt the said connection onclosing or immediately I before closing of the breaker.

In a second embodiment, these means are arranged so that they cause theclosing of the breaker before the spark plug is in a combustion chamberat the beginning of compression.

The invention also relates to monorotor rotary piston internalcombustion engines, characterized by the fact that they include anignition device such as defined above.

In order that the invention may be more fully understood, severalembodiments of ignition devices and engines according to the inventionare described below purely by way of illustrative but non-limitingexample, with reference to the accompanying drawings, in which:

FIG. I shows, diagrammatically, a first embodiment of a rotary pistoninternal combustion engine constructed according to the invention;

FIG. 2 shows, diagrammatically, a second embodiment of a rotary pistonengine constructed according to the invention; and

FIGS. 3 and 4 show certain elements of the embodiment of FIG. 2 in otheroperating positions; and

FIG. 5, lastly, shows a third embodiment.

In order to construct an ignition device for a rotary piston internalcombustion engine 1 comprising a casing 2 in the form of a trochoid withtwo lobes, provided with an intake port 3 and an exhaust port 4, and arotary piston 5 in the form of a curvilinear triangle with three crests5a, 5b, 5c, rotatable inside the said envelope (in clockwise directionaccording to FIGS. 1 and 2), the procedure is as follows.

First of all, regarding the assembly of the ignition device,conventionally it is made to include a DC. electrical voltage source 6constituted, for example, by a battery provided with a positive terminal14 and a negative terminal 7 connected to a common ground 8. Itincludes, preferably, two spark plugs 9 and 10 mounted in the envelopeof the casing 1 and shown diagrammatically in FIGS. 1 and 2. These twospark plugs are separated from one another along the periphery of theenvelope of the casing 2, so as to favor the establishment as rapidly aspossible of the flame front, over the whole length ofa chamber B whichoccurs at the end of compression and of which the shape, as seen inFIGS. 1 and 2, is very flattened and elongated. The spark plug 9 isoften called the top or upper plug. The spark plug 10 is called thebottom or lower plug. Each of these plugs include two electrodes ofwhich the first is connected to the ground 8 and of which the second isconnected in the manner indicated above.

To the two plugs 9 and 10, there is made to correspond, as shown in FIG.1, two induction coils 11 and 12 provided respectively with primarywindings 11a and 12a and with secondary windings 1 1b and 12b. Thewindings 11a and 11b have a common terminal 13 connected to the positiveterminal 14 of the voltage source 6 through an ignition switch 15. Thewindings 12a and 12b have also a common terminal 16 directly connectedto the terminal 13.

The primary winding 11a includes a second terminal 17 connected to theground 8 through a breaker 18 mounted parallel with a condenser 19. Inthe same way, the primary winding 12a includes a second terminal 20connected to the ground 8 by a second breaker 21 mounted parallel with asecond condenser 22.

The breaker 18 comprises a rigid conductor arm 23, hinged at one of itsends on a fixed axle 24 and bearing, at its other end, a conductivepastille 25, which pastille can come into contact with another fixedpastille 26 connected electrically to the ground 8. The pastille 25 isconnected electrically to the terminal 17 of the coil 11 through the arm23. The latter bears, substantially at its center, an insulatingfollower 27. The breaker 21 is identical with the breaker 18 and theparts of this breaker analogous to those of the breaker l8 bear the samereference numerals followed by the letter a. The pastille 25a isconnected electrically to the terminal 20 of the coil 12.

The two breakers l8 and 21 are arranged substantially symmetrically withrespect to the axis of rotation ofa cam 28 with two diametricallyopposite bosses 29 and 30. The said cam is driven in rotation at a speedproportional to that of the engine and co-operates with the followers 27and 27a of the breakers so as to allow to come into contact and toseparate alternately, on one hand, the pastilles 2S and 26, and on theother hand, the pastilles 25a and 26a. Flexible return means, not shown,act on the two arms 18 and 23. In the same way, adjusting means for theadvance of the spark (not shown) may act on the angular adjustment ofthe cam 28 with respect to the shaft of the engine which is moved by thepiston 5.

The secondary windings 11b and 12b include, respectively, outputterminals 31 and 32. Up to the present, these terminals were, in thecase of monorotor rotary piston engines, connected directly andpermanently to the second electrode of the plugs 9 and 10, respectively.It will be recalled that the first electrode of the said plugs isconnected to the ground 8.

The operation of such a conventional device was as follows.

When the rotary piston 5 arrives in a predetermined position to whichthere corresponds a volume also predetermined of the chamber B, the cam28 separates from one another, simultaneously or with a slightdisplacement in time, on one hand, the pastilles 25 and 26, and on theother hand, the pastilles 25a and 26a. There is hence a brusque openingof the electrical circuit of each primary winding 11a and 12a whichgenerates a considerable variation of magnetic flux in the said primarywindings. This magnetic flux variation induces in the secondary windings11b and 12b a high electrical voltage. The terminals 31 and 32 are thusbrought to a high potential with respect to the ground and it is thesame for the electrodes of plugs 9 and 10 respectively connected to theterminals 31 and 32. The assembly is constructed in such a way that thedifference of potential which appears between the electrodes of theplugs 9 and 10 is sufficient to produce a spark suitable for ignitingthe compressed mixture in the chamber B.

By reason of the rotation of the cam 28, the bosses 29 and 30 thereforeseparate from the followers 27 and 27a and the pastilles 25 and 26, 25aand 26a again come into contact with one another. There is closing ofthe primary circuit of each coil 11 and 12 and the intensity of thecurrent flowing in the coils 11a and 12a passes from a null value to anon-null value. Hence, on the closing of the primary circuit, avariation of magnetic flux is again produced in the primary windings 11aand 12a and a high difference of potential of the order of 1,500 to2,500 volts appears between the electrodes of the plugs 9 and 10. At themoment when the closing of the primary circuit of the coil 12 occurs,the lower plug 10, connected to this coil, is in the presence of gasunder high pressure and the dielectric strength of these gases is highenough for a spark not to flash generally between the electrodes of theplug 10. Even though a spark should flash, it would not be troublesomesince it would be produced in a mixture of burnt gases.

On the other hand, at the moment when the closing of the primary circuitof the coil 11 is produced, that is to say at the same time orsubstantially at the same time as the closing of the primary circuit ofthe coil 12, the crest 5a of the piston, which bounds the rear zone ofthe chamber B, has generally passed by the plug 9. The latter occursthen in a chamber containing a mixture of fresh gas at the beginning ofcompression. Most of the time, the difference of potential which appearsbetween the electrodes of the plug 9 is sufficient to generate a sparkand an untimely pre-ignition of a mixture which has not yet reached thedesired level of compression. The spark flashes fairly easily since themixture is little compressed and possesses hence a relatively lowdielectric strength. But such a preignition is troublesome to the goodoperation of the engine'and is accompanied by a noise similar to a loudclicking and a loss of power.

To overcome this drawback, according to the main feature of theinvention, there is made to include in the ignition device of the rotarypiston internal combustion engine 1, means to prevent the voltage peakof closing from appearing between the electrodes of each plug, when thelatter is in a combustion chamber at the beginning of compression.-

ln a first embodiment, the said means are constituted by a rotarycommutator 33 (FIG. 1) rotated by the engine 1 and which, on one hand,establishes an electrical connection between the plug 9 and the coil 11and between the plug 10 and the coil 12, slightly before and during theopening of the breakers 18 and 21, and on the other hand, interrupts thesaid connection slightly before and during the closing of the saidbreakers 18 and 21.

The rotary commutator 33 comprises a rotor 34 and a stator 35. The rotor34 is composed, on one hand, of a cylindrical crown of revolution 36,conductive at least over its periphery and provided with a radialconductor arm 37 extending towards the outside, on the other hand, of acylinder 38 conductive at least over its periphery, coaxial with thecrown 36 and provided with a radial conductor arm 39 diametricallyopposite the arm 37, a part of the cylinder 38 being situated on theinside of the said crown, and finally on the other hand, of an insulator40 arranged between the crown 36 and the cylinder 38. The position ofthe arm 39 along the axis of the rotor is such that said arm isinsulated electrically from the crown 36. The rotor 34 is driven aroundits axis at a speed proportional to that of the engine.

The stator 35, shown diagrammatically, bears the rotor 34 and comprisestwo brushes 41,42 and two conductive terminals 43,44 diametricallyopposite with respect to the center of the rotor. The brush 41 bears onthe outer surface of the cylinder 38 and permits electrical connectionto be ensured between the arm 39 and the terminal 32 to which this brushis connected. The brush 42 bears on the outer surface of the crown 36and ensures the passage of electrical current between the terminal 31,to which it is connected, and the arm 37. The terminals 43 and 44 arearranged so that the arms 37 and 39 come to their contact or a slightdistance from the latter on each turn of the rotor. These terminals areconnected respectively to the second electrodes of the plugs 9 and 10.

Finally, it must be specified that the angular displacement of the rotor34, the angular amplitude of the phase during which there is electricalconnection between the arms 37,39 and the terminals 43,44 and theprofile of the cam 28 are determined so that the said connection isestablished slightly before and during the opening of the breakers 18and 21, but is interrupted before the closing of the breakers.

The operation of such a device is as follows.

When the pastilles 25,26 and 25a,26a are separated from one another bythe action of the cam 28, the arms 37 and 39 are respectively inelectrical connection with the terminals 43,44 (FIG. 1) as has beenexplained and the voltage peak of opening is applied to the electrodesof the plugs 9 and 10, which causes the production of a spark, aspreviously explained.

When the pastilles 25,26 and 25a,26a come again into contact with oneanother, that is to say on the closing of the breakers 18 and 21, thearms 37 and 39 have turned and are no longer in electrical connectionwith the terminals 43 and 44. The voltage peak of closing is nottransmitted to the electrodes of the plugs 9 and 10 but appears betweenthe arms and the terminals. The distance separating the arms from theterminals 43,44 at this moment is sufficient so that a spark is notproduced between these elements.

With the rotary commutator 33, there is therefore eliminated anypossibility of a production of a spark at the plugs on the opening ofthe breakers 18 and 21 and pre-ignition is thus eliminated.

In another embodiment, the rotary commutator 33 can include only asingle arm 37 and be arranged only in the circuit of the upper plug 9,whilst the low plug 10 is directly connected to the terminal of theoutput 32 of the coil 12. In this case, the spark due to the closing ofthe breaker 21 is not systematically suppressed on the plug 10, but thisis not troublesome since this spark can only be produced in a mixture ofburnt gases. According to the rotary speed given to the rotor 34, theremay be provided one or two diametrically opposite terminals andconnected electrically between themselves, to come into contact with thesingle arm 37. 1

According to a second embodiment, the abovesaid means to prevent thevoltage peak of closing from appearing at the electrodes of each plug,when the latter is in a chamber at the beginning of compression, may beconstituted by a cam outline 23 such that the closing of the breakers l8and 21 is produced before the spark plug 9, and all the more so, theplug 10, are in a chamber at the beginning of compression.

In this embodiment, the terminals 31 and 32 of the secondary windings ofthe coils are directly connected to the electrodes of the plugs 9 and10, as in known ignition devices for rotary piston engine. But, byreason of the outline of the cam, when the breakers close, the crest 5abounding the rear zone of the chamber B has not yet passed by the upperplug 9. The voltage peak of closing is hence applied to the plugs beforethe peak 5a has passed by the plug 9, and a fortiori, the plug It). Thetwo plugs are again in the chamber B in the pres ence of burnt gasesunder high pressure, hence at high dielectric strength, little favorableto the flashing of a spark on closing, as explained above. In any case,the flashing of such a spark would not be troublesome since it would beproduced in burnt gases.

However, it is possible that a cam outline satisfactory for theconditions described is too angular to enable completely satisfactoryoperation.

In order to preserve a cam profile which is little angular and toobtain, however, an opening followed very nearly by the closing of thebreakers, in another embodiment, the abovesaid means are constituted,for each induction coil, by a second breaker (45 for coil 11, see FIG.2) mounted in parallel with the first breaker (18 for the coil ill) andcooperating with the same cam, the assembly being such that any periodduring which two breakers arranged in a same primary circuit of a coilare open simultaneously is followed by the closing of one of thesebreakers before the spark plug connected on this coil occurs in achamber at the beginning of compression.

In FIG. 2, there is shown very diagrammatically the ignition device.There is provided, for the upper plug 9, an assembly 46 comprising twobreakers 13,45 mounted in parallel. There may be provided, for the lowerplug 10, an assembly 47 identical with 46. However only a single breakercould be used for the plug 10 since the latter, by reason of itsposition on the envelope of the casing 2, occurs practically always inthe presence of burnt gases when the voltage peak of closing isproduced, even if there is only a single breaker in the primary circuitof the coil 12 and if the profile of the cam is not particularly abrupt.The two breakers l8 and 45 can cooperate with a same cam 8 with threebosses for example. I

The operation of such a device is as follows.

The explanation only bears on the operation of the ignition device ofthe plug 9 since the operation of the device of the plug It) is eitheridentical or conventional.

When the cam 48 occupies the position shown in FIG. 2, the breaker 118is open but the breaker 45 is closed. The primary circuit of the coil111 is closed and the magnetic flux produced by the primary winding issubstantially constant. No voltage peak is therefore induced between theterminals of the secondary winding lllb.

When the cam 49 arrives in the position shown in FIG. 3, the breaker 18still open is at the point of closing at the moment when the breaker 45is opened. The opening of the breaker d5 causes the opening of theprimary circuit Illa and the appearance of the voltage peak of openingat the secondary circuit 111) and at the plug 9. At the moment when thisopening is produced, the level of compression in the chamber B hasreached a predetermined value, the spark flashes and normal ignitiontakes place.

Shortly after, when the cam 48 arrives in the position shown in FIG. 4and before the crest 5a has passed by the plug 9, the breaker 18 isclosed as well as the primary winding circuit 11a. The peak voltage ofclosing is hence produced before the plug 9 occurs in a combustionchamber at the beginning of compression and containing a mixture offresh gas.

With such a device, the outline of the cam can be normal since theinterval of time separating the opening and the closing of a samebreaker can be relatively great, whilst the interval of time separatingthe opening and the closing of the primary circuit is very slight.

As a result of which, and whatever the embodiment adopted, there isobtained an ignition device for a rotary piston engine which respondswell to the purpose for which it is proposed, namely to obtainundisturbed combustion cycles and to eliminate the pre-ignition ofmixtures of fresh gases at the beginning of compression. In the case ofthe first embodiment where there is introduced a rotary commutator inthe ignition device, pre-ignition is eliminated by eliminating the sparkof closing. In the case of the second and third embodiments,pre-ignition is eliminated by establishing the closing of the breakerbefore the upper plug 9 has been passed by the crest 5a and occurs in achamber at the beginning of compression.

The operation of the rotary piston engine provided with such a device isimproved and the power of the said engine is held substantially constantin the course of operation.

As is self-evident, and as results besides already from the precedingdescription, the invention is in no way limited to those of its methodsof application, nor to those of its methods of production of its variousparts, which have been more particularly described; it embraces, on thecontrary, all variations.

In another embodiment, for example, the means of connection and ofdisconnection to prevent the voltage peak of closing from appearingbetween the electrodes of the spark plug, when the latter occurs in achamber at the beginning of compression, can be electronic.

In a further embodiment, illustrated in FIG. (wherein correspondingelements to those in FIG. 1 are identified by the same referencenumbers), the lower spark plug 10 can be directly connected to theterminal 32 of the plug 12, whilst, in the circuit of the upper plug 9,the rotary commutator 33 is replaced by a device with a disruptiveeffect 49 constructed, on one hand, so

as to allow an electrical current to pass when the voltage at itsterminals is of the order of the voltage produced by the secondary 11bat the opening of the breaker 18, that is to say of the order of 15,000to 20,000 volts, and on the other hand, so as to oppose the passage ofan electrical current when the voltage at its terminals is of the orderof 1,500 to 2,500 volts, an order of magnitude of the voltage obtainedon the closing of the breaker 18. This device 49 with disruptive effectcan, also, be incorporated in the plug.

What we claim is:

l. A monorotor rotary piston internal combustion engine comprising, asingle housing having a multilobed inner peripheral surface, a singlemultilobed rotor mounted for rotation within said housing, said housingcomprising an intake port and an exhaust port; in combination with anignition system comprising, a breaker, a cam driven by the engine andcooperating with the breaker, an induction coil having a primary circuitand a secondary circuit and at least two spark plugs on said peripheralsurface and connected to said secondary circuit operating together, thesecond said spark plug being located between the first said spark plugand said exhaust port, said breaker causing, particularly on opening butalso on closing of the primary circuit of the coil, a voltage peak ofopening and of closing respectively at the terminals of said secondarycircuit, and interrupting means in said secondary circuit adapted toprevent the voltage peak only of closing of the breaker from appearingat the electrodes of at least said first spark plug when the latter isin a combustion chamber of the engine at the beginning of compression.

2. An engine according to claim 1, wherein said interrupting means areconstituted by a second breaker mounted in parallel with the first andcooperating with a cam, the assembly being such that any period duringwhich the two breakers .are opened simultaneously is followed by theclosing of one of the breakers bypassing the voltage surge to the sparkplug before the spark plug is in a combustion chamber at the beginningof compression.

3. An engine according to claim 2, wherein said two breakers arearranged to cooperate with the same cam having three bosses.

4. An engine according to claim 1, wherein said interrupting means onlyact on said first spark plug, the second spark plug which on closing isin the burnt gases being directly connected to the secondary circuit.

5. An engine according to claim 1, wherein said interrupting means arearranged, on one hand, to establish an electrical connection between thespark plug and the secondary of the coil on opening or immediatelybefore opening of the breaker, and on the other hand, to interrupt saidconnection on closing or immediately before closing of the breaker.

6. An engine according to claim 1, wherein said interrupting means arearranged so that they cause the closing of the breaker before the sparkplug is in a combustion chamber at the beginning of compression.

7. An engine according to claim 1, wherein said interrupting means areconstituted by a rotary commutator rotated by the engine and havecontacts arranged to establish electrical connection between the sparkplug and the coil, slightly before and during the opening of thebreaker, and to interrupt said connection slightly before and during theclosing of the breaker.

8. An engine according to claim 1, wherein said interrupting means aresensitive to the voltage at the terminals of the secondary and areconstituted by a device with a disrupting effect allowing an electricalcurrent to pass when the voltage at its terminals is of the order of thevoltage which appears at the terminals of the secondary of the coil onthe opening of the breaker, that is to say of the order of 15,000 to20,000 volts, and opposing the passage of an electrical current when thevoltage at its terminals is of the order of the voltage at the terminalsof the secondary on the closing of the breaker, that is to say of theorder of 1,500 to 2,500 volts.

9. An engine according to claim 8, wherein said device with a disruptingeffect is incorporated in said first spark plug.

10. An engine according to claim 1, wherein said interrupting means areconstituted by a portion of said cam having an outline of sudden slope.

1. A monorotor rotary piston internal combustion engine comprising, asingle housing having a multilobed inner peripheral surface, a singlemultilobed rotor mounted for rotation within said housing, said housingcomprising an intake port and an exhaust port; in combination with anignition system comprising, a breaker, a cam driven by the engine andcooperating with the breaker, an induction coil having a primary circuitand a secondary circuit and at least two spark plugs on said peripheralsurface and connected to said secondary circuit operating together, thesecond said spark plug being located between the first said spark plugand said exhaust port, said breaker causing, particularly on opening butalso on closing of the primary circuit of the coil, a voltage Peak ofopening and of closing respectively at the terminals of said secondarycircuit, and interrupting means in said secondary circuit adapted toprevent the voltage peak only of closing of the breaker from appearingat the electrodes of at least said first spark plug when the latter isin a combustion chamber of the engine at the beginning of compression.2. An engine according to claim 1, wherein said interrupting means areconstituted by a second breaker mounted in parallel with the first andcooperating with a cam, the assembly being such that any period duringwhich the two breakers are opened simultaneously is followed by theclosing of one of the breakers by-passing the voltage surge to the sparkplug before the spark plug is in a combustion chamber at the beginningof compression.
 3. An engine according to claim 2, wherein said twobreakers are arranged to cooperate with the same cam having threebosses.
 4. An engine according to claim 1, wherein said interruptingmeans only act on said first spark plug, the second spark plug which onclosing is in the burnt gases being directly connected to the secondarycircuit.
 5. An engine according to claim 1, wherein said interruptingmeans are arranged, on one hand, to establish an electrical connectionbetween the spark plug and the secondary of the coil on opening orimmediately before opening of the breaker, and on the other hand, tointerrupt said connection on closing or immediately before closing ofthe breaker.
 6. An engine according to claim 1, wherein saidinterrupting means are arranged so that they cause the closing of thebreaker before the spark plug is in a combustion chamber at thebeginning of compression.
 7. An engine according to claim 1, whereinsaid interrupting means are constituted by a rotary commutator rotatedby the engine and have contacts arranged to establish electricalconnection between the spark plug and the coil, slightly before andduring the opening of the breaker, and to interrupt said connectionslightly before and during the closing of the breaker.
 8. An engineaccording to claim 1, wherein said interrupting means are sensitive tothe voltage at the terminals of the secondary and are constituted by adevice with a disrupting effect allowing an electrical current to passwhen the voltage at its terminals is of the order of the voltage whichappears at the terminals of the secondary of the coil on the opening ofthe breaker, that is to say of the order of 15,000 to 20,000 volts, andopposing the passage of an electrical current when the voltage at itsterminals is of the order of the voltage at the terminals of thesecondary on the closing of the breaker, that is to say of the order of1,500 to 2,500 volts.
 9. An engine according to claim 8, wherein saiddevice with a disrupting effect is incorporated in said first sparkplug.
 10. An engine according to claim 1, wherein said interruptingmeans are constituted by a portion of said cam having an outline ofsudden slope.